1. Field of the Invention
The invention relates in general to an image sharpening apparatus, and more particularly to an image sharpening apparatus capable of enhancing sharpness of an image according to an edge intensity of the image.
2. Description of the Related Art
Digital images captured by various optical devices, such as a camera or a scanner, have lowered sharpness due to various factors including, for example, poor designs of the optical devices, the digital image processing procedures, or shakes occurred when the cameras are capturing images. Thus, the digital image usually has to be sharpened so that the sharpness of the image is enhanced. The conventional image sharpening method, such as an unsharp masking method, is to locally lighten brighter portion of an edge region and to locally darken darker portion of the edge region so that the sharpness of the image is enhanced. However, the conventional image sharpening method cannot distinguish image edge from noise. Thus, the conventional image sharpening method not only enhances the sharpness of the image but also amplifies the noise in the image so that the overall image quality is deteriorated.